Term Index (I)
- I:
- I band: photometric filter for near infrared light
- I Zw 18:
- I Zwicky 18 (I Zw 18,Zw I 18): blue compact galaxy with low metallicity
- I Zw 36:
- I Zwicky 18 (I Zw 18,Zw I 18): blue compact galaxy with low metallicity
- i-band:
- IAA:
- IAC:
- IACT:
- Iapetus:
- moon: a planet's natural satellite, such as Earth's
- Saturn: second largest planet in the solar system
- IAU:
- IAU Circular:
- IAU galactic coordinate system:
- IAUC:
- IBAS:
- INTEGRAL: European gamma ray observatory-satellite
- IBEX:
- IBEX-Hi:
- IBEX-Low:
- IBIS:
- INTEGRAL: European gamma ray observatory-satellite
- IC:
- Index Catalog (IC): 1895 catalog of galaxies, star clusters, and other nebulae
- IC 342: spiral galaxy in the Council of Giants
- IC 342/Maffei Group:
- IC 342: spiral galaxy in the Council of Giants
- ICAT:
- ICE:
- ice dwarf:
- ice giant: planet more massive than gas planets and less than rocky planets
- ice line:
- snow line: distance from protostar cool enough for water to condense
- ice transition radius:
- snow line: distance from protostar cool enough for water to condense
- IceCube: neutrino detector at the South Pole
- IceCube Neutrino Observatory:
- IceCube: neutrino detector at the South Pole
- ICEMAG:
- ICF:
- ICM:
- ICRF:
- ICRF3:
- ICRS:
- idea gas law:
- Hayashi limit: limit on the temperature of a star dependent upon its mass and luminosity
- ideal gas:
- ideal gas law: relates pressure, temperature, and volume
- IDFT:
- IDL: interactive vector-oriented programming language
- IDP:
- IDS:
- IDV:
- IEO:
- IFS:
- IFTS:
- IFU:
- IFU Observation:
- IFU spectroscopy:
- IGAPS:
- IGAS:
- Ulysses: space mission to observe the Sun from off the ecliptic
- IGM:
- IGR:
- INTEGRAL: European gamma ray observatory-satellite
- II:
- III:
- illumination: measure of light energy producing a telescope's image
- Illustris Project: 2013-2015 series of cosmological simulations
- IllustrisTNG Project:
- IMAGE: satellite mission to study magnetosphere
- IMACS:
- image dissector:
- image dissector photomultiplier:
- image plane:
- focal plane: plane within optical system at which an image is in focus
- image scale:
- plate scale: relation between angle and distance across an image
- image slicer:
- image stabilization: camera mechanism to compensate for movement
- image stacking:
- stacking: combining images of the same object
- Image-Dissector Scanner:
- imager:
- Imager for Magnetopause-to-Aurora Global Exploration:
- IMAGE: satellite mission to study magnetosphere
- imaging:
- imaging atmospheric Cherenkov telescope:
- imaging Fourier transform spectrometer:
- imaging Fourier transform spectroscopy (IFTS): Michelson-interferometer-based imaging spectroscopy
- imaging spectrograph:
- imaging spectrometer: device to capture spectrum point-by-point of an image
- spectroscopy: measurement of light with various electromagnetic wavelengths
- IMAPS:
- IMB: 1980s neutrino detector
- IMBH:
- IMF:
- immersion grating: grating where light is within the material
- IMPACT:
- impact: collision of one solid body with another
- STEREO: two-satellite system to observe the Sun
- impact erosion:
- impact: collision of one solid body with another
- impact parameter:
- impacts:
- IMPS:
- IRAS: 1983 satellite that surveyed the sky in infrared
- IMRI:
- IMS:
- Giotto: 1980s space mission carrying out a Comet Halley flyby
- IMXB:
- in situ: on site
- in situ observation:
- INAF:
- incidence:
- inclination:
- inclination-type resonance:
- orbital resonance: tendency of orbits of multiple bodies to remain in a simple pattern
- Index Catalog (IC): 1895 catalog of galaxies, star clusters, and other nebulae
- Index Catalog of Visual Double Stars:
- Index Catalogue of Nebulae and Clusters of Stars:
- Index Catalog (IC): 1895 catalog of galaxies, star clusters, and other nebulae
- index of refraction:
- twinkling: blinking, apparent movement and color changes of observed stars
- India:
- Indian Initiative in Gravitational-wave Observations:
- LIGO-India: planned gravitational wave detector in India
- INDIGO:
- LIGO-India: planned gravitational wave detector in India
- inertial forces:
- Reynolds number (Re): measure reflecting a fluid system's propensity to turbulence
- inertial frame of reference:
- inertial mass:
- mass: object's quality that determines the effects of forces and gravity
- inertial reference frame: frame of reference where no force means no acceleration
- inertial wave: type of wave in a rotating fluid
- infall:
- inferior planet:
- infinitesimal transform:
- infinitesimal transformation:
- inflated gas giant:
- hot Jupiter (HJ): Jupiter-sized gas exoplanet orbiting very close to star
- inflated radii: exceptionally large radii of some hot Jupiters
- inflation: theorized rapid expansion of the very early universe
- inflation field:
- inflation theory:
- inflation: theorized rapid expansion of the very early universe
- inflationary theory:
- inflation: theorized rapid expansion of the very early universe
- information:
- infrared (IR): electromagnetic radiation, wavelength 0.74-300 micrometers
- AFGL Four Color Infrared Sky Survey (AFGL): 1970s infrared survey
- AKARI: Japanese space infrared telescope
- ARIEL: planned space mission for exoplanet spectrography
- Atacama Submillimeter Telescope Experiment (ASTE): ten meter submillimeter telescope in Chile
- AtLAST: plan for submillimeter telescope in Chile
- BOOMERanG: 1990s-2000s balloon-borne 1.3-meter millimeter telescope
- Canada-France-Hawaii Telescope (CFHT): 3.6 meter optical/infrared telescope in Hawaii
- Catalog of Infrared Observations (CIO): collection of infrared observation data from numerous sources
- CCAT: 25-meter submillimeter telescope plan for Chile
- Cerro Tololo Inter-American Observatory (CTIO): NOAO observatory in Chile with Blanco telescope
- chopping mirror: internal pivoting mirror to slightly change the instrument's aim
- Cosmic Background Explorer (COBE): 1989 satellite for observing the CMB
- cosmic infrared background (CIB,CIBR): widespread infrared radiation not associated with known sources
- CRIRES: high resolution IR echelle spectrometer
- Darwin: past plan for space telescopes acting as an interferometer
- electromagnetic spectrum: spectrum of EMR
- ESO 3.6m Telescope: reflector telescope at La Silla
- Euclid: planned observatory-satellite to measure dark energy
- European Southern Observatory Very Large Telescope (ESO VLT,VLT): four 8.2-meter optical telescopes in Chile that can act together
- far infrared (FIR,far-IR): infrared radiation with wavelengths in the 30-450 μm range
- FINESSE: planned space mission for exoplanet spectrography
- Fred Lawrence Whipple Observatory (FLWO): observatory near Amado, Arizona
- Fred Young Submillimeter Telescope (FYST,CCAT-p): planned 6-meter submillimeter telescope in Chile
- Gaia: 2010s astrometry survey satellite
- Galileo Observatory: infrared observatory-plane in the early 1970s
- Gemini Observatory: pair of telescopes in Hawaii and Chile
- Gemini Planet Imager (GPI): infrared instrument to overcome signal noise imaging exoplanets
- Gran Telescopio Canarias (GTC): 10.4 meter telescope in the Canary Islands
- Herschel Space Observatory: infrared observatory-satellite with 3.5 meter reflector
- High Definition Space Telescope (HDST): proposed 12 m space telescope
- Hubble Space Telescope (HST): observatory-satellite with 2.4 meter reflective telescope
- hyperluminous infrared galaxy (HLIRG, HyLIRG): a galaxy emitting a more far infrared than an ULIRG
- I band: photometric filter for near infrared light
- infrared cirrus: cirrus-cloud-like infrared emissions from dust, etc.
- infrared dark cloud (IRDC): molecular cloud not emitting nor transmitting infrared
- infrared excess (IRX): more infrared than that of a star's typical spectrum
- Infrared Space Observatory (ISO): 1990s 60-cm infrared space telescope
- Infrared Survey Facility (IRSF): 140 cm reflector telescope that images in infrared
- Infrared Telescope Maffei (ITM,IRAIT): 80 cm infrared telescope in Antarctica
- IOTA: past optical interferometer in Arizona
- IPAC: Caltech group to collect and analyze infrared observations
- IRAS: 1983 satellite that surveyed the sky in infrared
- IRSA: archive center for infrared data from NASA missions
- IRTF: Mauna Kea 3-meter infrared telescope
- James Clerk Maxwell Telescope (JCMT): far-infrared telescope in Hawaii
- James Webb Space Telescope (JWST): future space-based 6.5 meter infrared telescope
- K band: atmospheric window centered around 2.2 microns, or 136 THz
- Keck Observatory: observatory in Hawaii with two 10-meter reflectors
- Kitt Peak National Observatory (KPNO): NRAO observatory in Arizona with Mayall telescope
- Kuiper Airborne Observatory (KAO): infrared observatory-plane in the 1980s
- Large Binocular Telescope (LBT): dual 8.4 meter telescope in Arizona
- Large Millimeter Telescope (LMT): large microwave telescope in Mexico
- LiteBIRD: planned spacecraft to map CMB polarization
- low-surface-brightness galaxy (LSB galaxy): galaxies less bright than those historically identified
- Lowell Discovery Telescope (LDT,DCT): 4.3 m telescope at Lowell Observatory, Arizona
- luminous infrared galaxy (LIRG): a galaxy emitting a lot of far-infrared light
- LUVOIR: plan for a space-based telescope
- Magellan Telescopes: pair of 6.5 m optical telescopes in Chile
- MAXIMA: 1998-1999 balloon-borne 1.3-meter millimeter telescope
- mid infrared (MIR,mid-IR): infrared radiation with wavelengths in the 7.5-25 μm range
- Midcourse Space Experiment (MSX): 1990s space telescope
- Mimir: multi-function near-infrared instrument on Perkins Telescope
- Munich Near-Infrared Cluster Survey (MUNICS): 1990s-2000s galaxy cluster survey
- near infrared (NIR,near-IR): electromagnetic radiation in the range of 800-2500 nm
- New Technology Telescope (NTT): 3.58-meter reflector telescope in Chile
- NIRPS: near-infrared extension to HARPS spectrograph
- obscured fraction-luminosity relation: relation between AGN luminosity and surrounding dust IR emission
- OH/IR source: AGB star with strong OH maser
- OIR: a spectral "band name" for both visible light and infrared
- Origins Space Telescope (OST): concept for future very large space IR telescope
- R band: band of visible light around 6500 angstroms
- Roman Space Telescope (RST,WFIRST): proposed near-infrared space observatory
- SCUBA: submillimeter instrument on James Clark Maxwell Telescope
- SOFIA: aircraft-based infrared observatory
- SpeX: a medium-resolution infrared spectrograph
- SPICA: plan for a future space IR telescope
- SPIRou: CFHT spectropolarimeter for exoplanet research
- Spitzer Extragalactic Representative Volume Survey (SERVS): infrared survey of some well-studied fields
- Spitzer Space Telescope (SST): past a satellite with infrared telescope
- starburst galaxy: galaxy forming stars at a very high rate
- Subaru Telescope: 8.2 meter telescope in Hawaii
- submillimeter galaxy (SMG): galaxy that produces significant submillimeter radiation
- Submillimeter Telescope (SMT,HHSMT): 10 meter far-infrared telescope
- Telescopio Nazionale Galileo (TNG): 3.58 m telescope in Canary Islands
- TripleSpec (TSpec): near-infrared spectrograph on the Hale Telescope
- Two Micron All-sky Survey (2MASS): near-infrared survey of both hemispheres
- Two Micron Sky Survey (IRC,TMSS): 1969 infrared catalog produced by Caltech
- UKIDSS: five-part infrared survey using UKIRT
- ultraluminous infrared galaxy (ULIRG,ELF): a galaxy emitting a more far infrared than an LIRG
- United Kingdom Infrared Telescope (UKIRT): Mauna Kea 3.8 meter infrared telescope
- University of Tokyo Atacama Observatory (TAO): observatory for a 6.5 m infrared telescope under construction
- UVOIR: a spectral "band name" covering UV, visible light, and IR
- VISTA: 4.1 meter telescope in Paranal Observatory in Chile
- Wide Field Infrared Explorer (WIRE): partly-failed 1999 infrared satellite
- William Herschel Telescope (WHT): 4.2 meter telescope in the Canary Islands
- Infrared Astronomical Satellite:
- IRAS: 1983 satellite that surveyed the sky in infrared
- infrared astronomy:
- infrared (IR): electromagnetic radiation, wavelength 0.74-300 micrometers
- Infrared Catalog:
- infrared cirrus: cirrus-cloud-like infrared emissions from dust, etc.
- infrared dark cloud (IRDC): molecular cloud not emitting nor transmitting infrared
- infrared excess (IRX): more infrared than that of a star's typical spectrum
- Infrared Imaging Surveyor:
- AKARI: Japanese space infrared telescope
- infrared light:
- infrared (IR): electromagnetic radiation, wavelength 0.74-300 micrometers
- infrared luminosity:
- infrared (IR): electromagnetic radiation, wavelength 0.74-300 micrometers
- Infrared Optical Telescope Array:
- IOTA: past optical interferometer in Arizona
- Infrared Processing and Analysis Center:
- IPAC: Caltech group to collect and analyze infrared observations
- Infrared Science Archive:
- IRSA: archive center for infrared data from NASA missions
- Infrared Space Observatory (ISO): 1990s 60-cm infrared space telescope
- Infrared Survey Facility (IRSF): 140 cm reflector telescope that images in infrared
- Infrared Telescope Facility:
- IRTF: Mauna Kea 3-meter infrared telescope
- Infrared Telescope Maffei (ITM,IRAIT): 80 cm infrared telescope in Antarctica
- infrared window:
- ING:
- Ingenuity:
- Mars 2020: Mars rover launched in July 2020 and on its way
- ingress duration:
- INGRID:
- initial fluctuation spectrum: the power spectral density of the early universe
- initial fluctuations: early universe density variations leading to current universe
- initial mass function (IMF): function describing initial mass of stars
- INMS:
- Cassini: explorer spacecraft sent to Saturn
- inner cloud:
- Hills cloud: cloud of comets and minor planets around the solar system
- inner Lindblad resonance:
- inner moon:
- Enceladus: Saturn moon considered possible carrier of life
- inner Oort cloud:
- Hills cloud: cloud of comets and minor planets around the solar system
- inner working angle:
- coronagraph: telescope feature to block light from a specific body
- inner-Earth object:
- innermost stable circular orbit (ISCO): border of region surrounding a BH in which orbits are unstable
- INS:
- neutron star (NS): stellar remnant consisting entirely of solar masses of neutrons
- insolation: solar energy received per unit area in given time
- instability region: region around an object where orbits cannot persist
- instability strip: region of H-R diagram where stars are unstable
- Institut de radioastronomie millimétrique (IRAM): organized radio astronomy collaboration between France, Germany, and Spain
- Institut für Theoretische Astrophysik:
- Institute for Pale Blue Dots:
- Institute for Theoretical and Experimental Physics:
- Institute of Theoretical Astrophysics (ITA): Heidelberg research institute
- Instituto de Astrofísica de Canarias (IAC): research institute on Canary Islands
- instrument:
- 4MOST: spectrograph in development for VISTA telescope
- ACBAR: instrument used in CMB search
- ACIS: imaging spectrometer on Chandra X-ray telescope
- Air-SPEC: spectrometer used to view the corona during eclipses
- ASPIRE: mechanism to stabilize observations from an airplane
- CAPMAP: early 2000s array that surveyed CMB polarization
- CONCERTO: spectrometer aimed at mapping the [CII] line
- CorMASS: near-infrared spectrograph
- COSMOSOMAS: microwave survey
- CRIRES: high resolution IR echelle spectrometer
- Dark Energy Spectroscopic Instrument (DESI): new instrument for measuring red-shift of distant objects
- eROSITA: Russian/German space X-ray telescope launched in 2019
- G-CLEF: spectrograph on the GMT
- Gemini Planet Imager (GPI): infrared instrument to overcome signal noise imaging exoplanets
- GISMO: 2 mm bolometer camera on IRAM 30 m telescope
- GUPPI: radio-telescope back-end aimed at processing pulsar data
- HARMONI: spectrograph planned for E-ELT
- HARPS: high-precision spectrograph for exoplanet searches
- HARPS-N: high-precision spectrograph for exoplanet searches in Canary Islands
- HERMES: four-channel spectrograph on the Anglo-Australian Telescope
- Keck Planet Finder (KPF): spectrograph in development for Keck
- Keck Planet Imager and Characterizer (KPIC): extreme AO upgrade under development for Keck
- KMOS: 2-micron spectrograph on ESO VLT
- linearly variable filter (LVF): filter whose passband varies over one spatial dimension
- MICADO: camera planned for E-ELT
- Mimir: multi-function near-infrared instrument on Perkins Telescope
- Multi-object Optical and Near-IR Spectrograph (MOONS): advanced spectrograph under development for VLT
- MUSTANG: bolometer array on the Green Bank Telescope
- NEWS: planned near-infrared spectrometer on Discovery Channel Telescope
- NIRPS: near-infrared extension to HARPS spectrograph
- PAMELA: cosmic ray detector attached to satellite
- phase plate: filter that changes the phase of light passing through
- plate measuring machine (APM): machine to measure position of images on photographic plates
- POLARBEAR: instrument to map CMB polarization
- PUPPI: Arecibo radio-telescope instrument aimed at observing pulsars
- QUEST: sixteen square-degree survey camera
- RELIKT-1: instrument on 1980s Soviet satellite to view the CMB
- SCUBA: submillimeter instrument on James Clark Maxwell Telescope
- SpeX: a medium-resolution infrared spectrograph
- SPHERE: VLT instrument for imaging exoplanets
- SPIRou: CFHT spectropolarimeter for exoplanet research
- TAIPAN: multi-object spectrograph with robot fiber-positioner
- TolTEC: sensitive infrared camera under construction for the LMT
- Tomographic Ionized-carbon Mapping Experiment (TIME): proposed instrument to map the [CII] line
- TripleSpec (TSpec): near-infrared spectrograph on the Hale Telescope
- waveplate: type of optical device that alters polarization
- WEAVE: spectrograph under construction for the William Herschel Telescope
- Wide-field Multi-object Spectrograph (WFMOS): proposed instrument to detect baryon acoustic oscillations
- instrument type:
- instruments:
- INT:
- INT Galactic Plane Survey:
- INT Photometric H-alpha Survey of the Northern Galactic Plane:
- INT Photometric Halpha Survey:
- INTEGRAL: European gamma ray observatory-satellite
- INTEGRAL Burst Alert System:
- INTEGRAL: European gamma ray observatory-satellite
- integral field spectrograph: spectrograph that captures images
- integral field spectrometer:
- integral field spectroscopy:
- integral field unit (IFU): instrument to allow a spectrograph to capture data over a 2D field
- integrated Sachs-Wolfe effect:
- integration time: time required to acquire signal
- intensity: power reaching a surface from a specific source
- radiance: measure of EMR to/from a solid angle through and area
- intensity interferometer:
- intensity map:
- intensity mapping: measure of cosmic matter density
- interacting binary:
- interacting galaxy:
- galactic tide: effect of one galaxy's gravity, such as on another galaxy
- Interactive Data Language:
- IDL: interactive vector-oriented programming language
- intercloud gas:
- interference: result of interaction of waves
- interference pattern:
- interferometer: device detecting properties of electromagnetic waves by detecting interference between waves
- interferometry: analysis of superimposed EMR waves
- intergalactic clouds:
- Lyman-alpha forest: overlaid redshifted Lyman-alpha absorption lines on light from distant objects
- intergalactic dust: dust not within galaxies
- intergalactic medium (IGM): matter between galaxies
- interloper:
- intermediate band photometry:
- photometry: studying starlight through bandpass filters
- intermediate mass ratio inspiral:
- intermediate polar:
- intermediate spiral galaxy:
- intermediate-mass black hole:
- intermediate-mass X-ray binary:
- intermediate-velocity cloud:
- internal gravity wave: ripples in a change in density in a fluid
- internal wave:
- International Astronomical Union (IAU,UAI): association of professional astronomers
- International Atomic Time:
- terrestrial time (TT): current measure of time for astronomical observations on Earth
- International Celestial Reference Frame:
- International Celestial Reference System (ICRS): standardized variation of equatorial coordinate system
- International Cometary Explorer (ICE): 1980s space mission flying by comets
- International Gamma-ray Astrophysics Laboratory:
- INTEGRAL: European gamma ray observatory-satellite
- International Pulsar Timing Array (IPTA): organization of pulsar timing arrays
- International Robotic Antarctic Infrared Telescope:
- International Solar Polar Mission:
- Ulysses: space mission to observe the Sun from off the ecliptic
- International Space Station:
- EUSO-SPB: balloon-born cosmic ray observatory
- MAXI: Japanese X-ray camera on the International Space Station
- NICER: space X-ray mission specifically to view neutron stars
- International Sun-Earth Explorer:
- International System of Units:
- International Ultraviolet Explorer (IUE): 1980s ultraviolet space telescope
- International Virtual Observatory Alliance:
- interplanetary dust:
- cosmic dust: cosmic dust is dust in space such as interstellar dust
- interplanetary dust cloud:
- cosmic dust: cosmic dust is dust in space such as interstellar dust
- interplanetary dust particle:
- interplanetary magnetic field:
- interplanetary medium (IPM): matter in the solar system around and between planets
- interpretation:
- CO to H2 factor (Xco,XCO): assumed ratio between observed CO emission lines and H2 mass
- interstellar astronomy:
- interstellar astrophysics: astronomy of the ISM including dust and clouds
- Interstellar Boundary Explorer (IBEX): satellite observing the ISM/heliosphere boundary
- interstellar cloud:
- cloud: higher-density region of space
- interstellar dust:
- cosmic dust: cosmic dust is dust in space such as interstellar dust
- interstellar extinction:
- extinction: the absence of any radiation from an astronomical object because all is absorbed or scattered
- interstellar holography: holographic analysis of incoming EMR to study the intervening ISM
- interstellar magnetic field (ISMF): galactic magnetic field between that of stars
- interstellar matter:
- interstellar medium (ISM): matter within a galaxy between star systems
- shell: hollow shaped region of some kind of ISM
- supershell: very large ISM shell-shaped region
- Interstellar Medium Absorption Profile Spectrograph (IMAPS): 1980s/1990s UV spectrometer
- interstellar planet:
- field: adjective meaning "in this field of view but unrelated"
- interstellar reddening:
- reddening: red appearance of astronomical objects because blue light is attenuated by dust
- interstellar scintillation:
- intertropical convergence zone (ITCZ): circulation pattern near equator where north and south Hadley cells meet
- intracluster gas:
- intracluster medium (ICM): hot plasma throughout a galaxy cluster
- intraday variable:
- intrinsic color index:
- color index: a number that characterizes the color of an object
- intrinsic S-star:
- S-type star (S): type of star with lines indicating zirconium
- intrinsic variable:
- inverse beta decay:
- inverse bremsstrahlung:
- bremsstrahlung: photon emission when a charged particle is decelerated
- inverse Compton:
- Compton scattering: photon collision with a charged particle that emits a different photon
- inverse Compton scattering:
- inverse discrete Fourier transform:
- inverse Fourier transform:
- Fourier series: type of series able to approximate a periodic function
- Fourier transform (FT): systematic method of breaking down functions into periodic components
- inverse model:
- forward model: model producing potential observable values from parameters
- inverse Radon transform:
- tomography: observation of sections of a 3D object
- inverse square law: a value's dependency upon reciprocal of the square of the distance from something
- inverse volume weighting:
- Io: well-known Jupiter moon
- Io plasma torus:
- Io: well-known Jupiter moon
- Io torus:
- Io: well-known Jupiter moon
- ion: non-neutral atom or molecule, with missing or extra electrons
- ion engine: type of electrical spacecraft engine
- Dawn: explorer spacecraft sent to asteroids Vesta and Ceres
- ion thruster:
- ionic bond:
- adsorption: adhesion to a surface
- ion: non-neutral atom or molecule, with missing or extra electrons
- oxidation state: number of electrons loaned out by an atom in an ionic bond
- ionic ocean:
- ionization:
- ionization correction factor (ICF): relations between ion abundances and element abundances
- ionization energy:
- ionization fraction: a substance's ratio of unattached electrons to nuclei
- ionization front:
- ionization potential: energy needed to ionize an atom
- ionization state:
- ionization temperature:
- ionization valve:
- kappa mechanism (κ-mechanism): stellar instability caused by opacity increasing with temperature
- ionize:
- ionized carbon fine structure line ([CII]): carbon line that traces distant star formation
- ionized carbon forbidden line:
- ionized hydrogen (HII,H II): state of hydrogen when sufficiently hot
- ionized interstellar medium:
- ionizing radiation: radiation with photon energy sufficient to ionize
- ionosphere: layers of Earth atmosphere with significant ions
- space weather: varying conditions in space affecting Earth and humans
- ions:
- IOTA: past optical interferometer in Arizona
- IPAC: Caltech group to collect and analyze infrared observations
- IPC:
- HEAO-2: 1978 X-ray observatory space mission
- IPHAS: H-alpha survey
- IPM:
- IPMO:
- IPTA:
- IPTA+:
- iPTF:
- IR:
- infrared (IR): electromagnetic radiation, wavelength 0.74-300 micrometers
- IR excess:
- infrared excess (IRX): more infrared than that of a star's typical spectrum
- IR SFR:
- IR star formation rate:
- IRAC:
- IRAIT:
- IRAM:
- IRAM 30m Millimeter Radio Telescope:
- IRAM 30m Telescope: millimeter-range radio telescope in Sierra Nevada, Spain
- IRAS: 1983 satellite that surveyed the sky in infrared
- IRAS 16293-2422:
- IRAS Faint Source Catalog:
- IRAS: 1983 satellite that surveyed the sky in infrared
- IRAS Minor Planet Survey:
- IRAS: 1983 satellite that surveyed the sky in infrared
- IRAS Point Source Catalog:
- IRAS: 1983 satellite that surveyed the sky in infrared
- IRAS-FSC:
- IRAS: 1983 satellite that surveyed the sky in infrared
- IRAS-PSC:
- IRAS: 1983 satellite that surveyed the sky in infrared
- IRC:
- IRCAM:
- IRCS:
- IRD:
- IRDC:
- IREM:
- INTEGRAL: European gamma ray observatory-satellite
- iridium:
- IRIS:
- AKARI: Japanese space infrared telescope
- Thirty Meter Telescope (TMT): extremely large telescope planned for Hawaii
- Voyager: space probes to observe planets and the edge of the solar system
- IRIS2:
- IRMS:
- iron (Fe): metal, Fe, atomic number 26
- iron core collapse:
- core collapse: results when the center of something loses its pressure
- iron Kα:
- iron K-line:
- iron peak: relatively high abundance of iron and nearby elements
- iron star:
- exotic star: term for theoretical stars not made of atoms/ions
- iron-56:
- nickel (Ni): metal, Ni, atomic number 28
- IRPOL:
- Irr-I:
- Irr-II:
- irradiance: EMR power reaching a surface
- irregular:
- irregular galaxy: galaxy that's not a disk or ellipsoid
- irregular moon: moon with an atypical orbit, such as retrograde
- irregular satellite:
- irregular variable:
- IRS:
- IRSA: archive center for infrared data from NASA missions
- IRSF:
- IRTF: Mauna Kea 3-meter infrared telescope
- IRTS:
- Irvine-Michigan-Brookhaven detector:
- IMB: 1980s neutrino detector
- IRX:
- infrared excess (IRX): more infrared than that of a star's typical spectrum
- IS☉IS-EPI:
- ISAAC:
- Isaac Newton Group of Telescopes (ING): three telescopes in Canary Islands
- Isaac Newton Telescope (INT): 2.5 m telescope in Canary Islands
- iSALE: code modeling the shock physics of impacts
- ISAMS:
- ISCO:
- ISCO-radius:
- ISEE:
- ISEE-3:
- iSEEP Wide-Field MAXI:
- MAXI: Japanese X-ray camera on the International Space Station
- ISEM:
- ISG:
- ISGRI:
- INTEGRAL: European gamma ray observatory-satellite
- iShell:
- IRTF: Mauna Kea 3-meter infrared telescope
- ISIS:
- ISM:
- ISM cirrus:
- ISMF:
- ISO:
- ISO spectrum:
- ISOCAM:
- isochrone:
- H-R diagram (HRD): diagram relating effective temperature to luminosity
- ISOHDFS:
- isolated galaxy:
- isolated neutron star:
- neutron star (NS): stellar remnant consisting entirely of solar masses of neutrons
- isolated planetary mass object:
- isolation mass: mass of an oligarch after accreting all nearby planetesimals
- isolation mass core:
- isolation mass: mass of an oligarch after accreting all nearby planetesimals
- isolation mass planet:
- isolation mass: mass of an oligarch after accreting all nearby planetesimals
- ISOPHOT:
- isophote: line on a diagram indicating a level of brightness
- Holmberg radius (RH,RHO): a measure of size of galaxy based on surface brightness
- isostasy: crust-mantle equilibrium
- isothermal core: core region of a body of all the same temperature
- isotope: subclass of an element with a specific number of nucleons
- 1H: hydrogen isotope with no neutrons
- deuterium (D,2H): hydrogen isotope with one neutron
- isotope fractionation:
- isotope notation:
- isotope: subclass of an element with a specific number of nucleons
- isotope signature:
- isotopes:
- element: class of atom based on its number of protons
- isotopic fractionation:
- isotropic radiant energy:
- isotropic radiation:
- isotropy: uniformity in all directions
- ISPM:
- Ulysses: space mission to observe the Sun from off the ecliptic
- ISS:
- Cassini: explorer spacecraft sent to Saturn
- EUSO-SPB: balloon-born cosmic ray observatory
- NICER: space X-ray mission specifically to view neutron stars
- scintillometry: measuring of twinkling
- Voyager: space probes to observe planets and the edge of the solar system
- ISW:
- IsWe:
- ITA:
- Italian:
- Italian National Institute of Astrophysics:
- Italian Robotic Antarctic Infrared Telescope:
- Italian Space Agency:
- Italy:
- ITCZ:
- ITEP:
- ITEP-SAI Supernova Light Curve Catalogue: online catalog
- iterative method:
- ITM:
- IUE:
- IUE Data Analysis Center:
- IUEDAC:
- IUV:
- MAVEN: Mars orbiter to study its atmosphere
- Ivanov:
- IVC:
- iWF-MAXI:
- MAXI: Japanese X-ray camera on the International Space Station
- Ixion:
Index